Which of the following is the quantity of diluent the pharmacy technician should combine with a 5 mL vial containing 500 mg of azithromycin to achieve a final concentration of mg/mL?

To determine the correct quantity of diluent needed to achieve a desired concentration of azithromycin, we start with the information provided: a 5 mL vial contains 500 mg of azithromycin. First, we need to calculate the desired final concentration in mg/mL.

The initial concentration of the azithromycin in the vial can be calculated as follows:

• Concentration = Total amount of drug / Volume of solution

• Concentration = 500 mg / 5 mL = 100 mg/mL

If the goal is to find out how much diluent to add to achieve a different final concentration, we need a specific target concentration. Assuming the aim is to dilute the solution and that the correct choice is aimed at achieving a certain final concentration, we can determine how much diluent is necessary.

In this case, if we want to dilute to a concentration of 100 mg/mL, adding 1.5 mL of diluent would bring the total volume to 6.5 mL. Then the concentration would still be derived but would reflect the dilution:

• New concentration = Total drug / New total volume

• New concentration = 500 mg / 6.5 mL

The correct answer indicates that